Tumour necrosis factor (TNF) is a homotrimeric cytokine produced by numerous cell types, including monocytes and macrophages, that was originally identified based on its capability to induce the necrosis of certain mouse tumor. TNF is one of the principal mediators of the immune and inflammatory response, and it is e.g. known to have an important role in the pathogenesis of rheumatoid arthritis, which is a common autoimmune inflammatory disease that affects approximately 0.5-1% of the human population. Additionally, TNF is also known to be involved in the pathogenesis of a wide range of disease states, including endotoxin shock, cerebral malaria and graft-versus-host reaction. The soluble and bioactive form of TNF consists of three identical 17 kD protein subunits (homotrimeric), whereas the membrane bound form consist of three identical 26 kD subunits.
Recombinant or modified proteins are an emerging class of therapeutic agents. To date, several recombinant or modified proteins which acts as TNF antagonists have been disclosed. In particular, antibodies that bind to and neutralise TNF have been sought as a means to inhibit TNF activity. Infliximab (Remicade) and Eternarcept (Enbrel) are examples of two TNF antagonists which have both received marketing authorization in the United States and Europe for treatment of rheumatoid arthritis. The two products have also been shown to be effective for the treatment of psoriasis and Chrohn's disease. Infliximab is a chimeric antibody with murine variable regions and human IgG1 and κ constant regions, which neutralises the biological activity of TNF by binding to the soluble and transmembrane forms of TNF and inhibits the binding of TNF with its receptors. The structure of Infliximab is similar to that of naturally occurring antibodies. Eternacept is a fusion protein made up of the extracellular domain of the p75 TNF receptor and the hinge and Fc domains of human IgG1.
WO 2004/0398 discloses four specific binding polypeptides based on human tetranectin C-type lectin like domains (CTLD) which are capable of binding TNF. The proteins are differing from the wild-type CTLD by the amino acid sequence KVRSRYF in the loop 1 region (tetranectin amino acids nos. 116-122 in SEQ ID NO:79), and PRHT, PTNN, PTNR, or PNNR in the loop 3/4 region (tetranectin amino acids nos. 146-149 in SEQ ID NO:79) (cf. WO 2004/0398, Table 4, page 46).
The present inventors have identified and isolated specific TNF binding proteins based on human tetranectin C-type lectin like domains with improved binding characteristics and improved efficacy. The identified TNF binding proteins are superior to the above prior art CTLD based TNF binding proteins i.a. in terms of their in vivo capability of inhibiting and neutralising TNF. This has e.g. been demonstrated by their capability to inhibit TNF alpha mediated cytotoxicity in a murine fibroblast cell line assay, as will be apparent from the following examples. Additionally, the isolated specific TNF binding proteins have also been demonstrated to have superior TNF antagonistic characteristics as compared to the commercially available TNF antagonists Infliximab (Remicade) and Eternarcept (Enbrel).